Tanks transport a large variety of dangerous and toxic chemicals on our roads, waterways and railways. A number of different valve systems are used in association with these tanks. In some cases, the valve requires manual operation, and the failure to maintain a tension on a cable associated with the valve results in the valve closing. In certain other tanks, the valve opening means "cams over" to an open position, where it remains locked unless and until the "cam over" position is defeated. While this defeat of the locked open position is often accomplished manually by the pulling of a cable affixed to the valve, new regulations are soon going to require that the valve be equipped with a thermally-active means to defeat the locked position and automatically close the valve, as in the case of a fire where a manual operator cannot physically approach the tank to pull the cable. When such a thermally-active means is provided, the valve should still maintain the ability to be manually closed through the pulling of the cable. In other words, the automated system is intended to be available in addition to and certainly not in lieu of the manual system.
While the "cam over" type loading/unloading valves are useful on a variety of tanks and the like, they are the most common type of valve used in association with intermodal tanks. An intermodal tank is the tank version of a container transport. A rectangular frame generally surrounds a cylindrical tank in the intermodal configuration. This frame may be easily lifted and transported on board a ship, as well as being placed on a truck trailer or a rail car. The loading/unloading valve is typically positioned at the bottom rear of the tank, and the cable to release the "cam over" feature is routed down one of the edges of the tank frame. While the device of the present invention is described as being particularly used with an intermodal tank, it will, of course, be obvious that it would be useful in association with other types of tanks. It is therefore an advantage of the present invention to provide a valve with a cam locking the valve in an open position with a thermally-active closing means which reverses the cam action by pulling a cable, while leaving the cable still manually operable.